Androids and satellites aren't just science-fiction soulmates. The two came together on Friday when Sirius XM Radio (Nasdaq: SIRI) introduced an application for smartphones powered by Google's (Nasdaq: GOOG) Android operating system.

This is welcome news, even if it's entirely expected.

Sirius XM introduced a streaming app for Apple (Nasdaq: AAPL) iPhones and web-connected iPods last year. A similar program debuted for Research In Motion's (Nasdaq: RIMM) BlackBerry owners four months ago.

Android represents a logical expansion target for the satellite radio giant's mobile streaming strategy. In April, there were more Android-powered smartphones sold in this country than iPhone devices. Android is giving hardware manufacturers an economical launching pad, and they're coming through with a wide array of iPhone alternatives.

This isn't all good news for Sirius XM bulls. Do you know how many paying subscribers are streaming Sirius or XM through their iPhones and BlackBerrys? Neither do I. Sirius XM may be chatty about the number of total subscribers it gains or the successful upsells of its "Best of" premium packages, but it has been surprisingly quiet about the number of stand-alone streaming accounts.

That silence is a mixed blessing. On the one hand, smartphone owners are a generally affluent crowd, and they should have no problem forking over another $13 a month for satellite-radio streams -- less, if they're existing satellite-based customers. On the other hand, they've already got access to Internet radio and music discovery sites for free. It also doesn't help that some of Sirius XM's star attractions, including Howard Stern and some live sports, aren't available through the streaming apps.

Satellite radio has been a big seller at the automotive level, where users' alternatives usually boil down to terrestrial radio or a CD player. Smartphone owners have far more options. They may also want to keep their smartphones free for actual calls, email, or light cybersurfing. Some may not want to drain their smartphone batteries or carry around audio earbuds.

Should we celebrate Sirius XM's arrival on the fast-growing Android platform? Absolutely. The move brings satellite radio more incremental subscribers, and puts its foot in the right door. In the unlikely event that Sirius XM one day decides to replace costly satellites with a streaming model, it'll need to be a force on every smartphone platform. However, this is little more than a niche offering until Sirius XM tells us otherwise.

Do you stream Sirius or XM through your smartphone? Share your experiences in the comment box below.

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Longtime Fool contributor Rick Munarriz is a subscriber to both Sirius and XM. He does not own shares in any of the stocks in this article. He is also a member of the Rule Breakers analytical team, seeking out the next great growth stock early in its defiance. The Fool has a disclosure policy.